Metallurgy



NOV- 26, 1963 c. A. scHRoER ETAL. 3,111,732

METALLURGY Filed Jan. 50, 1958 3 Sheets-Sheet 2 INVENTORS. CHARLES A. SCHROER DALE C SWANSON FREDER/CK STEEDLY ATTOR NGV' 26, 1963 c. A. scHRoER ETAL 3,111,732

METALLURGY 3 Sheets-Sheet 5 Filed Jan. 50, 1958 INVENTORSA CHARLES A. SCHROER DALE C. SWA/VSON FEEDER/CK STEEDLV ATTO United States Patent O 3,111,732 METALLURGY Charles A. Schroer and Dale C. Swanson, Spokane, Wash.,

and Frederick Steedly, Ravenswood, W. Va., assignors to Kaiser Aluminum & Chemical Corporation, Oakland,

Calif., a corporation of Delaware Filed Jan. 30, 1958, Ser. No. 712,157 2 Claims. (Cl. 22-2flQ) This invention relates to the handling of molten metal prior to the casting thereof. More particularly, this invention relates to a method and system for transfer of molten metal from a source thereof, e.g. furnace or other molten metal holding receptacle, to a mold and which is effective in eliminating or substantially reducing the presence of foreign material in the molten metal supplied to the mold and reducing the gas content thereof.

In the casting of metals, e.g. aluminum and aluminum alloys, it is common practice to provide a body of molten metal in a suitable holding receptacle, eg. oil, gas, coal or coke fired open hearth or reverberatory furnace, electrical resistance heated furnace or induction heated furnace. The molten metal is generally fluxed in the holding receptacle and then transferred from the holding receptacle to the casting station. While in some instances the relative positions of the casting station and furnace may be such as to permit the molten metal to flow directly from the furnace into the casting station, it is common to find the furnace spaced a given distance away from the casting station and use made of a transfer trough or troughs for conveying the molten metal to the casting station. For example, the molten metal may pass from the holding receptacle directly into a long transfer trough by level-pouring through the long trough, down through an underpour outlet and into the casting mold. A further example involves use of a short transfer trough intermediate the holding receptacle and long trough wherein the molten metal passes into the short trough and through an underpour outlet into the long trough.

ln general each outlet is provided with control means such as a rod positioned within the outlet for controlling the rate of flow of molten metal through the outlet at a predetermined desired rate by Varying the position of the rod. The lower end of this rod will be referred to hereinafter as the control point. The predetermined desired rate of flow of molten metal through the outlet depends on many factors. Where continuous or semicontinuous casting is employed the rate of flow of molten metal through the outlet is directly dependent on the drop rate, i.e. casting rate. he drop rate in turn is dependent on many factors such as composition of the metal being cast, size of the ultimate cast body, type of casting etc. The selection of the desired rate of flow may be made with a minimum of trial and error by those skilled in the casting art.

Such practice possesses certain inherent disadvantages with regard to the presence of inclusions and porosity in the ultimate cast body. ln conventional practice, there may be an appreciable quantity of particulate material in the molten metal issuing from the furnace such as particles of refractory material from the furnace linings and dross particles which pass into the casting mold and result in inclusions in the ultimate cast body.

Further, as the metal begins pouring out of an underpour outlet, feeding metal into a transfer trough or into the mold itself, the metal will fall through the air until the liquid level in the mold or trough, as the case may be, rises to a level suiciently high to cover the lower end of the underpour outlet. During this period there is a tendency for entrapment of gases and moisture in the molten metal. In addition any falling of molten metal through the air and splashing of molten metal 3`,l l 1,7 Patented Nov. 26, 1963 lCe results in the formation of oxide particles which become inclusions in the ultimate cast body. Even after the level of the molten metal rises suiciently high to cover the lower end of the underpour outlet it has been found that there is considerable stirring action in the vicinity of the outlet which tends to stir in the dross and impurities which normally float on the surface of the molten metal, and the heavy impurities which normally lie on the bottom of the trough or container. In addition it has been found that there is a tendency of entrapment of gases and moisture in the molten metal when the level of the molten metal on the outside of the underpour outlet is below the control point, i.e., the lower end of the control means within the outlet. The exact cause of this moisture and gas entrapment is not known. However, it is believed that when the level of molten metal outside the underpour outlet is below the control point a partial vacuum is created below the lower end of the control rod and the pressure differential forces the gases and moisture in the atmosphere surrounding the outlet into this zone of partial vacuum either through pores in the outlet or downwardly along the control rod.

ln accordance with prior art practice screening has been employed to remove particles from molten metal which may become inclusions in the ultimate cast body. These prior art screening practices have effected substantial improvements in the quality of the ultimate cast bodies produced. However, such practices often fail to remove the finely divided inclusions as required in the production of very high quality material, and at the same time permit the dow rates presently employed in the casting of aluminum metal bodies.

These inherent disadvantages of the prior art practices have given rise to excessive production losses through scrapping of castings due to inclusions and porosity.

Accordingly, the primary purpose and object of this invention is to provide an improved method and means for handling molten metal prior to casting which eliminates or substantially reduces many of the disadvantages of the prior art techniques.

Another object of this invention is to provide a novel method and system for eliminating or substantially reducing defects such as porosity or inclusions in cast bodies.

Another object of this invention is to provide a system for handling molten metal prior to casting bodies therefrom including means for the elimination or substantial reduction of the presence of inclusions in such bodies.

Another object of this invention is to eliminate or substantially reduce the presence of such defects as porosity and inclusions in cast aluminum metal bodies by the use of a method and means whereby finer mesh screening is employed in the treatment of the molten aluminum metal prior to casting than possible in the prior art.

Another object of this invention is to provide a system and method for filtering molten aluminum prior to casting bodies therefrom including means for filtering very fine particles at rapid flow rates.

Other objects and advantages of this invention will be apparent from the following description thereof in conjunction with the accompanying duawings.

ln accordance with this invention, molten metal is transferred from a source such 4as a holding receptacle to a casting mold lby means of at least one downwardly directed underpour outlet through which the molten metal passes into the casting mold. The molten metal passing into the casting mold is 'filtered :through a screening surface surrounding this outlet. This screening surface comprises a `glass cloth filter bag `disposed around the outlet with the open end of the bag affixed around the neck of the outlet in a manner such that molten metal may not overflow the upper edge of the bag. Accordingly, all

the molten metal passing through the outlet must fiow through the glass cloth. Since the molten met-al is prevented from overflowing the upper edge of the filter, a pressure or head ysubstantially higher than employed in prior ant practices may be employed for forcing the molten metal through the filter.

Where conventional screening techniques are employed the maximum pressure which may be employed is that equivalent to a head of molten metal equal -to the difference between the height of the molten metal outside the screen contained in the casting mold and the height of the upper edge of the screen. Where greater pressures are employed with prior art techniques the molten metal overows the upper edge of the screen. By the use of the glass cloth filter bags embodying the principles of this invention it is possible to effectively employ a head of the molten metal greater than in the prior art. Thus a filter cloth may be employed having openings of a concentration and size sufficiently small to filter out the fine particles as required in the casting of high quality cast bodies such -as ingots for the production of aircraft plate, even when the molten metal flows through the outlet at a rapid rate. A filter cloth having a small size and concentration of openings, `as described above, restricts the molten metal flow sufficiently to support a head :of the molten metal greater than the difference between the height of the molten metal outside the filter bag and the height of the upper edge of the filter blag when the molten metal flows through the outlet 4at a predetermined desired rate. Accordingly, the filter bag is completely filled with molten metal whereby the molten metal level outside the underpour outet is always maintained albove the control point.

The `accompanying drawings illustrate a presently preferred embodiment of the molten metal handling system of this invention `and the presently preferred method of operation as applied to the casting of bodies commonly referred to as sheet ingots.

FIGURES 1 land 1A constitute a fragmentary longitudinal elevation, partly in section, of an elongated transfer trough `and molds with parts removed for purposes of clarity, illustrating the `application of the gllass cloth filter bags embodying the principles of thisl invention to the outlets of a long transfer trough.

FIGURE 2 is an enlarged cross sectional view of the pouring ltrough of FIGURE 1 taken along the line 2 2 of 'FIGURE 1.

FIGURE 3 is a further enlarged view of the outlet, glass cloth filter bag and distributor of FIGURE 1.

FIGURE 4 is a side elevational view of a glass cloth filter bag embodying the principles of this invention for application to an outlet for delivering molten metal into a distributor within a casting mold.

FIGURE 5 is a plan view of the glass cloth filter bag of FIGURE 4.

FIGURE 6 is a fragmentary longitudinal elevation, partly in section of the inlet end of an elongated transfer trough with parts removed for purposes of clarity illus-- vtr-ating the application of glass cloth filter bags embodying the principles of this invention to the inlet end of a transfer trough.

FIGURE 7 is an enlarged end elevational view partially in cross section of a pouring trough and glass cloth filter embodying the principles of this invention wherein `two glass cloth filter bags are employed without the use of a distributor.

FIGURE 8 is a plan view of a support frame for supporting a glass cloth filter bag Iaround the inlet of a transfer trough.

FIGURE 9 is a fragmentary longitudinal elevation, partly in section of Ithe inlet end of an elongated transfer trough with parts removed for purposes of clarity, illustrating the support of glass cloth filter bags about the inlet end of a transfer trough by means of the suppor-t frame of FIGURE 8.

Referring now to the drawings in which the same reference numerals have Ibeen applied to corresponding parts and in particular to FIGURES l, 1A, 2 and 3, the present invention involves the use of glass cloth filter bags 12 disposed Iaround an underpour outlet 4 for deliv ering molten metal 43 to a casting mold 32 for casting a solid metal body 48.

In general, casting operations of the type dealt with in this invention involve the transfer of molten metal 43 from a source or receptacle, e.g. furnace 19, to a casting mold or molds 32 and wherein use is made of an elongated transfer trough 1 for conveying the molten metal from the receptacle to the casting molds 32. The primary reason for the use of such transfer trough is because of the space difficulties encountered in attempting to place the casting yst-ation closely adjacent the furnace 19 such that the molten metal 43 could flow directly from the place of exit from the furnace into the casting station and because of the desirability of placing the casting station such that it can be supplied with molten metal 43 from a plurality of furnaces. 'Ihe embodiment of the apparatus of the invention shown in FIGURE 1 and 1A comprises a relatively short trough or receptacle 17 suitably attached in a sealed fashion to furnace 19 in communication with a tap hole 18. Receptacle I1.7 generally comprises a shell 22 of a suitable metal such as steel or cast iron and -a suitable refractory lining 20. At the end of receptacle 17, opposite the end attached to furnace 19, is a suitable control means such as a flow regulator 24 which generally comprises an externally threaded elongated member 25 mounted in threaded relationship within a nut member 26 which is supported by a suitable member 23. On the top of member 25 is a suitable turning handle `27 for moving member 25 upwardly or downwardly. Attached to the bottom of receptacle 417 is an underpour outlet 28 through which the molten metal passes from the source, eg. furnace 19 into the entry end of a long transfer trough 1. Outlet 28 is provided with a tapered or conical lower end portion such that upon movement of member 25 upward or downward with respect to the lower end portion of outlet 28 the rate of fiow of met-al can be increased or decreased, respectively.

While the use of a short transfer trough or receptacle 17 has been shown and described, it is to be distinctly understood that other means for transferring the molten metal from furnace 19 to long transfer trough 1 may be employed. For example, an underpour outlet similar to outlet 28 could be suitably attached in a sealed fashion directly to furnace 19 or long transfer trough 1 could be so designed as to be attached directly in a sealed fashion to tap hole 18 and level-pour the molten metal from the furnace into the transfer trough 1. Further, in some instances, the molten metal could be transferred from the holding receptacle or furnace 19 directly into a casting mold 32 by means of an underpour outlet similar to outlet 2S attached directly to receptacle or furnace 19.

Transfer trough 1 may be of conventional design with a metal shell 21 containing refractory lining 3 which defines a cavity 2 through which the molten metal passes from the entry end to the exit end of trough 1.

After the molten metal has entered trough 1 it flows toward the end furthest removed from the entry end and passes downwardly into casting molds 32 through the use of control means positioned within each underpour outlet 4 such as flow control regulators 29 which are similar to that hereinbefore described in connection with underpouring the metal into trough 1 from furnace 19. Each ow control regulator 29 generally comprises an externally threaded elongated member 34 mounted in threaded relationship within a nut member 35 which is supported by and affixed to a suitable member 36. With reference to FIGURE 2 it can be seen that member 36 includes vertical portions 37 and a horizontal portion 38. On the top of member 34 is a suitable turning handle 39 for moving member 34 upwardly or downwardly. At-

tached to the bottom of transfer trough 1 are underpour outlets 4 through which the molten metal passes into casting molds 32 disposed below underpour outlets 4. While three outlets are shown in FIGURE 1 it is within the scope of this invention to employ a greater or lesser number of outlets 4 depending on the number of molds 32. Outlets 4 are provided with tapered or conical lower end portions such that upon movement of members 34 upward or downward with respect to the lower end portion of outlets 4 the rate of flow of metal can be increased or decreased respectively.

Generally a suitable molten metal distributor 6 is disposed within each casting mold 32 directly below the respective underpour outlet 4, particularly in the casting of bodies of large cross-section. This distributor 6 is supported by suitable means such as vertical members 16 and horizontal members 33. The lower ends of vertical members 16 are afixed to distributor 6 by means of bolts 30 and nuts 31 while the upper ends are affixed to horizontal members 33 by suitable means such as welding. Horizontal members 33 are in turn supported by the upper edges of molds 32. With reference more particularly to FIGURES 2 and 3 it will be seen that distributor 6 comprises an elongated container 7 having an imperforate bottom 8 and an open top 9. Suitable openings are provided in either end and near the bottom of container 7 through which the molten metal 43 passes to enter the mold 32. By means of container 7 and openings 10 the molten metal 43 is directed horizontally toward the ends of the casting mold 32 for uniform distribution.

Since the casting apparatus forms no part of the present invention, further description of same is deemed unnecessary. However, it is to be noted that the invention is applicable to the handling of molten metal preparatory to casting in any type of casting apparatus, e.g. continuous casting, semi-continuous casting, use of closed bottom mold, etc. and wherein the cast body may take vari- :ous cross-sectional shapes, eg., solid, tubular, round, elliptical, square and polygonal shapes.

With reference more particularly to FIGURES 2 and 3 it will be seen that filter bags 12 are installed around the underpour outlets 4 with the open ends of the bags 12 affixed around the necks of the outlets 4 in a manner such that molten metal may not flow over the upper edges of the bags and accordingly must flow through the glass cloth. These filter bags may be fabricated in various ways, e.g. from two pieces of glass cloth cut into the desired shape and sewn together with glass thread. The resulting filter bag is then turned inside out before using. One means for atiixing the bags to the necks of the outlets comprises the use of wires 5 of suitable material such as steel, tightly wrapped around the tops of bags 12 and outlets 4 with the ends twisted together to form a tight connection. Preferably the wire should be wrapped around several times. In the alternative, a suitable clamp fabricated from a thin strip of metal could be employed in lieu of wire 5.

Where a distributor 6 of the configuration shown in FIGURES l, 2 and 3 is provided within casting mold 32 below the outlet 4, it is preferred that the filter bags 12 take the form shown in FIGURES 4 and 5 with a relatively narrow top portion 11 for surrounding outlets 4 and a wide lower portion characterized by elongated portions 13 adapted to fit within distributor 6 when the bag 12 is placed in the distributor. While bags 12 are shown and described as applied to the underpour outlets 4 of a long transfer trough 1, it is within the scope of this invention to apply such bags 12 to any outlet through which molten metal enters a casting mold 32. For example, an outlet connected directly to a molten metal holding receptacle such as furnace 19.

Where a system employing a long transfer trough 1 and a short transfer trough or receptacle 17 is employed and a maximum filtration is desired, it may in some instances be advantageous to surround the outlet 28 of said receptacle with a second glass lter bag 14. Filter bag 14 may be fabricated in a similar manner to filter bags 12 and may be affixed to outlet 28 in the manner illustrated in FIGURE 6 which is similar to that described for aixing bag 12 to outlets 4, i.e. by means of a suitable wire 15 wrapped around the filter bag 14 and outlet 28 or by other suitable means such as a clamp.

In some instances filter bag 14 need not be affixed to outlet 28 but instead may be supported by a suitable supporting frame 44 disposed around outlet 28 which support frame 44 is in turn supported by the upper edges of trough 1. With reference more particularly to FIG- URE 8, it will be seen that support frame 44 comprises a ring member 45 and legs 46 aflixed to ring member 45 by suitable means such as welding. Ring member 45 is adapted to be positioned around outlet 28 with legs 46 resting on the upper edges of trough 1. Filter bag 14 may then have its upper edges maintained on ring member 45 by means of spikes 47 disposed around ring member 45 on the upper surface thereof. Spikes 47 are passed through the openings in the cloth of the upper edges of filter bag 14 thereby maintaining upper edges of bag 14 on ring member 45 whereby bag 14 may be supported.

While the use of a single filter bag 12 around each outlet 4 has been shown and described, it is within the scope of this invention to employ in some instances a plurality of filter bags, one disposed inside the other. In accordance with one embodiment of this invention two such filter bags are employed without the use of a distributor as shown in FIGURE 7. According to this embodiment, the inner filter bag 12 is atiixed to the outlet 4 as described above. A second filterr bag 49' is then disposed outside filter bag 12. Filter bag 49 may be afiixed to outlet 4 in a manner similar to that for afxing filter bag 12 to outlet 4, or a suitable supporting frame 50 may be employed. Supporting frame 50 comprises two pairs of horizontal members 40 and 41. Members 41 are disposed across casting mold 32 on either side of outlet 4 and are supported by the upper edges of casting mold 32. Members 40 are affixed at right angles to members 41 by suitable means such as welding and are disposed on either side of outlet 4. Thus members 41 and 40 form a rectangle about outlet 4 from which filter bag 49 may be suspended. Suitable spikes 42 are provided extending directly upward from the upper surface of members 41 and 40 to maintain thte upper edges of bag 49 on the upper surfaces off members 41 and 40 in a manner whereby the spikes 42 pass through the openings in the cloth of the upper edges of bag 49.

One example of the practice of this invention pertains to the casting of three, -10 inch by 49 inch 7075 aluminum alloy ingots having a length on the order of inches at a drop rate of 31/2 inches per minute. Approximately 15,000 pounds of 7075 aluminum alloy were charged and melted in an oil fired open hearth furnace. The molten metal was stirred for about 5 minutes and sampled by spectrographic analysis. The composition of the melt was approximately 0.15% silicon, 2.49% magnesium, 1.55% copper, 5.65% zinc, 0.09% manganese, 0.19% chromium, 0.32% iron, 0.03% titanium and balance aluminum. The molten metal was iiuxed by a suitable method and means. The temperature of the .metal was on the order of 1290 F. The metal was underpoured from the furnace through an underpour outlet and a screening surface surrounding the outlet into one end of a transfer trough containing three outlets. This screening surface comprised a glass cloth filter bag disposed about the outlet with the open end of the bag supported by a suitable supporting frame as shown in FIGURE 9. The molten metal was then passed along the transfer trough to the `opposite end where it passed down through the three transfer trough outlets and a screening surface surrounding each of the trough outlets, into a distributor and from the distributor into the mold. The screening surfaces surrounding each of the ltrough outlets comprised a glass cloth filter bag disposed about the outlet Iwith the open end of the bag afiixed around the neck of the outlet by means of a wire as shown in FIGURESy 1, 2 and 3. The glass fiber cloth comprising all filter bags was the cloth designated SM 199 by Soule Mills of New Bedford, Mass. This cloth had about 140 openings per square inch, each opening being about .03 inch by .04- inch.

The 7075 aluminum alloy ingots produced above had excellent metallurgical properties and were satisfactory for the production of high quality products by rolling, forging or extrusion operations. The ingots were subjected to refiectoscope tests and evidence of inclusions or porosity was found to be within the limits set by sonic standards for 7075 plate.

Another example of the practice of this invention pertains to the casting of three 16 inch by 38 inch 3003 aluminum alloy ingots having a length on the order of 110 inches at a drop rate of 3 inches per minute. Approximately 18,000 pounds of 3003 aluminum alloy were charged land melted in an oil fired open hearth furnace. The molten metal was stirred for about 5 lminutes and sampled by spectrographic analysis. The composition of the melt was approximately 0.22% silicon, 0.011% magnesium, 0.16% copper, 0.04% zinc, 1.17% manganese, 0.01% chromium, 0.65% iron, 0.01% titanium and balance aluminum. v The molten metal was fluxed by a suitable method and means. The temperature of the metal was on the order of 1300 F. The metal was underpoured from the furnace through an underpour outlet and a Screening surface surrounding the outlet into one end of a transfer trough containing three outlets. This screening surface comprised a glass cloth filter bag disposed about the outlet with the open end of the bag supported by a suitable supporting frame as shown in FIGURE 9. The molten metal was then passed along the transfer trough to the opposite end Where it passed down through the three transfer trough outlets and a screening surface surrounding each of the trough outlets into a distributor and from the distributor into the mold. The screening surfaces surrounding each of the trough outlets comprised a glass cloth filter bag disposed about the outlet with the open end of the bag affixed around the neck of the outlet by means of a wire as shown in FIGURES 1, 2 and 3. The glass cloth comprising all filter bags was the cloth designated EM 77 by the Exeter Mills of Exeter, New Hampshire. This cloth had about 77 openings per square inch, each opening being about .03 inch by .06 inch.

The 3003 aluminum alloy ingots produced above had excellent metallurgical properties and were satisfactory for the production of high quality products by rolling, forging or extrusion operations.

Another example of the practice of this invention pertains to the casting of three 16 inch by 38 inch 3003 aluminum alloy ingots having a length on the order of 110 inches at a drop rate of 3 inches per minute. Approximately 418,000 pounds of 3003 aluminum alloy were charged and melted in an oil fired open hearth furnace. The molten metal was stirred for about 5" minutes and sampled by spectrographic analysis. The composition of the melt was approximately 0.21% silicon, 0.011% magnesium, 0.14% copper, 0.05 Zinc, 1.16% manganese, 0.01% chromium, 0.63% iron, 0.01% titanium and balance aluminum. The molten metal was fiuxed by a suitable method and means. The temperature of the metal was on the order of 1300 F. The metal was underpoured from the furnace through an underpour outlet and a screening surface surrounding the outlet into one end of a transfer trough containing three outlets. This screening surface comprised a glass cloth filter bag disposed about the outlet with the open end of the bag supported lby a suitable supporting frame as shown in FIGURE 9. The molten metal was then passed along the transfer trough to the opposite end where it passed down through the three transfer trough outlets and a pair of screening surfaces one disposed inside the other surrounding each of the trough outlets into the mold. The inner screening surfaces surrounding each of the trough outlets comprised a glass cloth filter bag disposed about the outlet with the open end of the bag affixed around the neck of the outlet by means of a wire. The outer screening surfaces cornprised a glass cloth filter bag disposed about ythe inner bag and suported by a suitable fra-me as shown in FIGURE 7. The glass cloth comprising all filter bags was the cloth designated EM 77 by the Exeter Mills of Exeter, New Hampshire. This cloth had about 77 openings per square inch, each opening being about .0-3 inch by .06 inch,

The 3003 aluminum alloy ingots produced above had excellent metallurgical properties and were satisfactory for the production of high quality products by rolling, forging or extrusion operations.

As used in the claims, the 'term aluminum is meant to cover high purity aluminum, commercial purity aluminum and `aluminum alloys.

While there has 'been sho-wn and described hereinabove certain presently preferred embodiments of this invention, it is to be understood that the invention is not limited thereto and that various changes, alterations and modifications can be made 'thereto without departing from the spirit and scope thereof as defined in the appended claims, wherein- What is claimed is:

1. A method of supplying a substantially gas-free, filtered stream of molten aluminum to Ia casting mold from a body of said molten aluminum which comprises passing molten aluminum downwardly from below the surface of said body into la transfer trough, passing molten aluminum from ybelow the surface of the aluminum in said transfer trough downwardly through a projecting underpour outlet, passing said molten aluminum from said underpour outlet through a flexible glass cloth filter bag and into said casting mold, said glass cloth filter bag being characterized by (A) having its open end disposed around and liquid sealed to said underpour outlet in such manner that molten aluminum cannot overflow the upper edge of Isaid bag,

(B) having insufficient open iarea to pass as much molten aluminum as said underpour outlet at a head above the bottom of the trough, and

(C) extending far enough below said underpour outlet to contact the molten aluminum in said casting mold.

2. The process of claim 1 further characterized in that said yfilter bag Iremoves particles with a major dimension larger than 0.03 yinch from said molen aluminum stream.

References Cited in the file of this patent UNITED STATES PATENTS 1,199,628 Stauffer Sept. 26, 1916 1,983,579 Ennor et al. Dec. 11, 1934 2,243,425 Junghans May 27, 1941 2,610,740 Hunter Sept. 16, 1952 2,754,556 Kilpatrick July 17, 1956 2,757,425 Duncan et al. Aug. 7, 1956 2,840,871 Gaffney July 1, 1958 2,876,509 Gardner Mar. 10, 1959 

1. A METHOD OF SUPPLYING A SUBSTANTIALLY GAS-FREE, FILTERED STREAM OF MOLTEN ALUMINUM TO A CASTING MOLD FROM A BODY OF SAID MOLTEN ALUMINUM WHICH COMPRISES PASSING MOLTEN ALUMINUM DOWNWARDLY FROM BELOW THE SURFACE OF SAID BODY INTO A TRANSFER TROUGH, PASSING MOLTEN ALUMINUM FROM BELOW THE SURFACE OF THE ALUMINUM IN SAID TRANSFER TROUGH DOWNWARDLY THROUGH A PROJECTING UNDERPOUR OUTLET, PASSING SAID MOLTEN ALUMINUM FROM SAID UNDERPOUR OUTLET THROUGH A FLEXIBLE GLASS CLOTH FILTER BAG AND INTO SAID CASTING MOLD, SAID GLASS CLOTH FILTER BAG BEING CHARACTERIZED BY (A) HAVILNG ITS OPEN END DISPOSED AROUND AND LIQUID SEALED TO SAID UNDERPOUR OUTLET IN SUCH MANNER THAT MOLTEN ALUMINUM CANNOT OVERFLOW THE UPPER EDGE OF SAID BAG, (B) HAVING INSUFFICIENT OPEN AREA TO PASS AS MUCH MOLTEN ALUMINUM AS SAID UNDERPOUR OUTLET AT A HEAD ABOVE THE BOTTOM OF THE TROUGH, AND (C) EXTENDING FAR ENOUGH BELOW SAID UNDERPOUR OUTLET TO CONTACT THE MOLTEN ALUMINUM IN SAID CASTING MOLD. 